The present invention relates generally to heating using microwave energy and more particularly to a system and method of microwave heating objects, for example, fast food products, in an automated, assembly line fashion, and to a specifically designed microwave oven assembly especially suitable for this use.
One problem which continues to plague any typical "fast food" restaurant is the inability to keep up with the rush hour crowds, specifically those which appear at lunch or dinner time. One way to handle this is to precook the food, for example, hamburgers, ahead of time. Another way, however, and from a standpoint of quality a preferred way, is to develop a faster way to cook the sandwiches and particularly a way which could be automated, actually fashioned after an assembly line, and yet a way which is uncomplicated and economical.
One solution of course is to use a microwave oven. However, conventional microwave ovens do not lend themselves to automation, especially as part of an overall assembly line. Quite to the contrary, a typical microwave oven requires the operator first to open the door of the oven, then insert the object, for example a tray of hamburgers, then close the door, and so on. Certainly, it can be seen that this approach can be cumbersome and time consuming and even unreliable.
Another solution is what is commonly referred to as a microwave tunnel, such as is shown in U.S. Pat. Nos. 3,983,356 issued Sept. 28, 1976 and 3,754,111 issued Aug. 21, 1973, and sometimes referred to an end load, which does in fact lend itself quite readily to a continuous conveyor type of assembly line operation. The objects to be heated can be placed on a conveyor and taken into the heating section of the tunnel through one open end and moved out of this section through an opposite open end. However, one problem with this type of system for use in the type of operation discussed above, that is, for use in the fast food industry, is that the tunnel openings would have to be too large for efficient operation, at least from an economical standpoint. Too much microwave energy would be lost through these openings in a microwave tunnel sufficiently large to handle relatively large articles such as trays of sandwiches and in any event most likely would be much too expensive and complicated in design. There are also cases where one or two of the transverse dimensions of the product to be microwave-treated is larger than the electrically largest possible transverse dimension of the continuously open end loads. This transverse dimension has a fixed limit when larger than this, uncontrolled microwave leakage will result.
As will be seen hereinafter, the present invention provides for a microwave oven assembly which is not complicated in design and which is not too costly to manufacture and yet one which is especially suitable for assembly line use and, at the same time, one which is energy efficient.